Radial piston pump and motor



United States Patent lnventor William K. Engel Peoria, Illinois Appl. No. 769,569

Filed Oct. 22, 1968 Patented Sept. 29, 1970 Assignee Caterpillar Tractor Co.

Peoria, Illinois a corporation of California RADIAL PISTON PUMP AND MOTOR 12 Claims, 2 Drawing Figs.

US. Cl 91/491, 91/497, 417/221 Int. Cl ..F01b 13/04, F04b 49/00, F0413 1/02 Field of Search 103/161, 161.9; 91/198-203; 230/177; 92/56 References Cited UNITED STATES PATENTS Braunwalder Hele-Shaw Ernst Eynard Strickland Henrichson.. Simmons FOREIGN PATENTS 4/1952 France Primary Examiner-William L. Freeh Attorney-Fryer, Tjensvold, Feix, Phillips and Lempio ABSTRACT: A variable displacement pump and motor of the radial piston type comprises a stationary housing having a rectangular control ring shiftably mounted therein to selectively control fluid flow. The control ring has a plurality of radially disposed cylinders rotatably mounted therein. The piston of each cylinder is attached in spokelike fashion to a rotor which in turn cooperates with a pintle valve for fluid displacement purposes.

Patented Sept. 29, 1970 3,530,768

Sheet 1 of 2 L k l\\\\\\\\\\\\\\\\\\\\ INVENTOR WILLIAM K. ENGEL BY 9% 4 4, Pug; d,

, ATTORNEYS Patented Sept. 29, 1970 3,530,768

Sheet 2 of2 INVENTOR I WILLIAM K. ENGEL ATTORNEYS BY 9& g anzj vii- RADIAL PISTON PUMP AND MOTOR Variable displacement pumps and motors of the radial piston type, such as those employed in reversible hydrostatic transmissions, require a high degree of structural integrity to enable them to operate efficiently over long periods of time. In addition, such pumps and motors must be constructed and arranged for expeditious assembly and disassembly for servicing and like purposes.

An object of this invention is to assure such desiderata by providing a radial piston pump and motor with substantially large and parallel bearing surface means between a shiftable control ring and housing thereof. Another feature of this invention further enhances the devices structural integrity, efficiency and serviceability by providing means formed on the control ring to positively retain the cylindrical sleeves of radially disposed cylinders against radial movement while yet permitting the sleeves to freely rotate within the control ring.

Other objects of this invention will become apparent from the following description and accompanying drawings wherein:

FIG. 1 is a cross-sectional view of a radial piston pump and motor taken on line I--l in FIG. 2; and

FIG. 2 is a sectional view of the radial piston pump and motor taken on line II-Il in FIG. 1.

Referring to FIG. 1, a rectangular housing has inner surface portions forming a closed chamber 11 having a control ring means 12 shiftably mounted therein. Suitable means (not shown) may be employed to shift the ring from the zero displacement position illustrated to either the left or right for pumping or motorizing purposes. For example, the closed portion of chamber 11 on the right side of the ring could be suitably pressurized and the closed chamber portion on the other side of the ring suitably depressurized to shift the ring leftwardly to selectively vary fluid displacement in a conventional manner. Reverse, rightward movement of the ring would function to cause reverse rotation in a motor or reverse flow in a pump of the radially disposed cylinders, hereinafter described.

It should be noted that the ring has a substantial rectangular cross section and comprises spaced, parallel and flat upper and lower bearing surfaces 13 and 14, respectively, which preferably extend thereacross at least one-half of the rings width. In the embodiment shown, such surfaces extend substantially across the full width of the ring to provide bearing surface means with mating surface portions formed on the housing. Such substantially large bearing surface means provide positive guide means for the ring and enhances the structural integrity of the device by positively stabilizing the ring and components associated therewith relative to the housing. In contrast thereto, conventional devices of this type depend upon line or limited surface contact between corresponding ring and housing members. Such prior art devices are prone to damage and inefficient operation due to undue vibratory and related adverse operating conditions.

It should be noted that ring 12 is preferably chamfered or otherwise suitably relieved at corners 15 (FIG. 1). Such relief precludes binding or like effects as between the ring and housing. It should be further noted that the ring has inner surface portions forming a cylindrical chamber therein and is normally centered around a fixed longitudinal axis X when the device is maintained in its zero displacement condition of operation. The ring assembly constitutes the only structure adapted for shifting movements relative to the fixed axis.

Referring to FIG. 2, the housing has end cover plates 16 and 17 suitably attached thereto by bolts 18 and 19, respectively, to fully enclose the working components of the device. Bolts 20 may be utilized to secure plate 16 to a pintle valve comprising the annular flange of a member 21 and a tubular member 22. The'stationary pintle valve may have two groups of fluid passages 23 and 24 formed therein with each group either functioning as a fluid inlet or an outlet in a conventional manner. Prior art patents, such as US. Pat. No. 3,274,946, fully disclose and explain the function of such a pintle valve and devices ofthis type.

A cylindrical rotor 25 is rotatably mounted on member 21 and has a spline connection 26 formed at one end thereof adapted to engage mating splines of a power input (pump) or output (motor) shaft (not shown). The rotor is preferably arranged to abut annular thrust bearing washers 27 and 28 to axially position and retain the rotor in the housing. A plurality of radially outwardly projecting spokes 29 (which could terminate in a piston-like configuration or contain a cylindrical bore) are welded or otherwise suitably secured to the rotor in spoke-like fashion and either extend into respective cylindrical sleeves 30 or encircle piston-like projections from a shoe or slipper to form a plurality of cylinders.

In the preferred embodiment, the spoke 29 terminates in a piston 31 (FIG. 1) having arcuate bearing surfaces formed therearound to compensate for varied alignment of the piston relative to its mating sleeve. In particular, upon shifting of the ring relative to the housing, such bearing surface permits the resulting noncoincident relationship of the axis of spoke 29 relative to the axis of sleeve 30. A passage 32 is formed in the spoke and is adapted to have fluid communicated therethrough upon reciprocatory movement of piston 31.

Control ring 12 (FIG. 2) has end cover plates 33 and 34 attached thereto in the manner illustrated to form a U-shaped chamber to fully enclose the cylinders along with rotor 25. A further novel feature of this invention is the provision of means formed on the control ring to prevent undue radial movement of sleeves 30 and to also positively guide rotary movements thereof. Such means preferably comprises annular flanges 35 and 36 formed on plates 33 and 34, respectively, to aid in defining recesses 37 and 38. Such recesses function to trap and retain arcuate bearing shoes 39 suitably secured to and forming the closed ends of their respective sleeves.

Recesses 37 and 38 will thus function to hold shoes 39 in substantial bearing contact with the inner surface portions of the control ring so that when rotor 25 is actuated centrifugal and related forces will not cause the shoes to abruptly contact the control ring. In addition, shifting of the ring during operation will not subject structures, such as washers 27 and 28, to undue stress due to the shifting of the axes of spokes 29 and sleeves 30 relative to each other. It should be further noted that each bearing shoe has a length taken in the direction perpendicular to longitudinal axis X which is substantially greater than the diameter of a respective sleeve 30 to provide substantial bearing surfaces.

In operation, rotation of rotor 25 will function to rotate the cylinders relative to control ring 12 and housing 10. In the neutral control ring position illustrated in FIG. 1 no fluid displacement will occur as between passage groups 23 and 24 since the pistons will not reciprocate. However, full rightward movement of the control ring in FIG. 1, for example, will function to laterally displace the longitudinal axis of the control ring relative to the fixed longitudinal axis X of the pintle valve, rotor and housing. Thus, when the device is used as a pump, rotation of rotor 25 will function to reciprocate pistons 31 relative to cooperating sleeves 30 to communicate pressurized oil or other suitable fluid between passages 23 and 24 in a conventional manner.

Shifting of the control ring fully leftwardly in FIG. 1 will function to reverse flow between the two groups of passages. It should be further noted that the device may be employed as a fluid motor by employing fluid passage 23 or 24 as the energy input and rotor 25 as the drive output.

I claim:

1. A variable displacement pump and motor of the radial piston type comprising a housing having inner surface portions defining a chamber therein, a plurality of cylinders radially disposed for rotation about a fixed longitudinal axis in a control ring means and said control ring means mounted between said housing and said cylinders and having inner surface portions defining a cylindrical chamber for guiding rotary movement of said cylinders therein, said control ring means shiftably mounted in the chamber of said housing in a direction perpendicular to said longitudinal axis, the invention comprising substantially parallel and spaced bearing surface means formed on substantial mating surface portions of said housing and said control ring means for positively guiding said control ring means when it is shifted relative to said housing and for stabilizing said pump and motor upon rotation of said cylinders, means affixed to said control ring means for continuously engaging and holding said cylinders in set radial positions against the inner surface portions of said control ring means during all phases of pump and motor operation, a cylindrical rotor mounted for rotation about said longitudial axis in said pump and motor, said cylinders each comprising a piston means secured to and extending radially outwardly from said rotor in substantially equally spaced relationship therearound and annular thrust bearing washers arranged between each end of said rotor and said housing.

2. The invention of claim 1 wherein the mating surface portions of said control ring means are flat and extend across at least one-half of the width of said control ring means, said width taken in a direction perpendicular to said longitudinal axis.

3. The invention of claim 1 wherein said control ring has a substantially rectangular cross-section.

4. The invention of claim 1 wherein said cylinders each comprise a cylindrical sleeve having an arcuate bearing shoe secured to the end thereof, each of said shoes arranged in abutting relationship with the inner surface portions of said control ring means.

5. The invention of claim 4 further comprising means formed on said control ring means for retaining and holding said arcuate bearing shoes against radial movement with respect to and in substantial contact with the inner surface portions of said control ring and for permitting said cylinders to rotate within said control ring means.

6. The invention of claim 4 wherein each of said bearing shoes has a length taken in a direction perpendicular to said longitudinal axis which is substantially greater than the diameter of a respective cylindrical sleeve.

7. The invention of claim 1 further comprising pintle valve means for selectively communicating fluid to said cylinders upon rotation of said cylinders.

8. In a variable displacement pump and motor of the radial piston type comprising a housing having inner surface portions defining a chamber therein, a control ring means shiftably mounted in the chamber of said housing and having inner surface portions defining a cylindrical chamber therein, and a plurality of cylinders radially disposed for rotation about a longitudinal axis in said control ring means, each of said cylinders terminating radially outwardly in an arcuate bearing shoe arranged in abutting relationship with the inner surface portions of said control ring means defining said cylindrical chamber, the invention comprising means formed on said control ring means for retaining and holding said arcuate bearing shoes against radial movement with respect to the control ring and in substantial contact with the inner surface portions of said control ring and for permitting said cylinders to rotate within said control ring means and a cylindrical rotor mounted for rotation about said longitudinal axis in said housing, said rotor comprising cylindrical means secured to and extending radially outwardly from said rotor in substantially equally spaced relationship therearound.

9. The invention of claim 8 further comprising annular thrust bearing washers arranged between each end of said rotor and said housing. p

10. ln a variable displacement pump and motor of the radial piston type comprising a housing having inner surface portions defining a chamber therein, a control ring means shiftably mounted in the chamber of said housing and having inner surface portions defining a cylindrical chamber therein, and a plurality of cylinders radially disposed for rotation about a longitudinal axis in said control ring means, each of said cylinders terminating radially outwardly in an arcuate bearing shoe arranged in abutting relationship with the inner surface portions of said control ring means defining said cylindrical chamber, the invention comprising means formed on said control ring means for retaining and holding said arcuate bearing shoes against radial movement with respect to the control ring and in substantial contact with the inner surface portions of said control ring and for permitting said cylinders to rotate within said control ring means and parallel and spaced bearing surface means formed on substantial mating surface portions of said housing and said control ring means for positively guiding said control ring means when it is shifted relative to said housing and for stabilizing said pump and motor upon rotation of said cylinders.

11. In a variable displacement pump and motor of the radial piston type comprising a housing having inner surface portions defining a chamber therein, a control ring means shiftably mounted in the chamber of said housing and having inner surface portions defining a cylindrical chamber therein, and a plurality of cylinders radially disposed for rotation about a longitudinal axis in said control ring means, each of said cylin-' ders terminating radially outwardly in an arcuate bearing shoe arranged in abutting relationship with the inner surface portions of said control ring means defining said cylindrical chamber, the invention comprising means formed on said control ring means for retaining and holding said arcuate bearing shoes against radial movement with respect to the control ring and in substantial contact with the inner surface portions of said control ring and for permitting said cylinders to rotate within said control ring means, said bearing shoes having a length taken in a direction perpendicular to said longitudinal axis which is substantially greater than the diameter of a respective cylinder.

12. In a variable displacement pump and motor of the radial piston type comprising a housing having inner surface portions defining a chamber therein, a control ring means shiftably mounted in the chamber of said housing and having inner surface portions defining a cylindrical chamber therein, and a plurality of cylinders radially disposed for rotation about a longitudinal axis in said control ring means, each of said cylinders terminating radially outwardly in an arcuate bearing shoe arranged in abutting relationship with the inner surface portions of said control ring means defining said cylindrical chamber, the invention comprising means formed on said control ring means for retaining and holding said arcuate bearing shoes against radial movement with respect to the control ring and in substantial contact with the inner surface portions of said control ring and for permitting said cylinders to rotate within said control ring means and pintle valve means for selectively communicating fluid to said cylinders upon rotation of said cylinders. 

